The overall objective of this NIH R21 research proposal is to develop a novel, generic drug delivery platform technology to enhance the half-life of peptide drugs, which we have named Molecular Release Depots. Molecular Release Depots consist of peptide drugs that are expressed as concatemers -multiple copies of a peptide therapeutic linked by peptides that are a cleavage site for a specific protease. This proposal is motivated by the fact that although over 200 peptide drugs are in clinical development, most of these drugs are rapidly cleared, which necessitates frequent injection of the drug, with high peak serum exposure and hence undesirable side-effects. The central hypothesis of this proposal is that peptide concatemers can be designed to have long half-life in vivo and optimal release kinetics of the active peptide from the concatemer and will thereby improve the efficacy of the drug and require less-frequent dosing as compared to the peptide. We have chosen the delivery of Glucagon like peptide-1 (GLP- 1) as a clinically relevant test case to establish proof-of-concept of the Molecular Release Depot platform technology, because GLP-1 analogs are a new class of drugs for treatment of type-2 diabetes but have a short half-life in vivo. The Molecular Release Depot technology is an elegant solution to this problem as it will increase the half-life of peptides in vivo and provide optimized degradation kinetics of the concatemers into active peptides, and thereby provide a formulation that only requires once-a-week injection with fewer side-effects. Although proof-of-principle will be established with GLP- 1 analogs, we note that Molecular Release Depots is a relevant platform technology for a range of peptide drugs. PUBLIC HEALTH RELEVANCE: The proposed research will develop a new bioengineered drug delivery system, termed Molecular Release Depots. Molecular release depots consist of multiple copies of a peptide drug that are linked to each other by a short peptide sequence that is recognized and cut by enzymes present in the body. We will prove this concept with a short peptide drug, GLP-1, which is used to treat type II diabetes, and show that delivering a peptide drug, not as a single copy, but as multiple copies that are linked together, has the potential to profoundly improve the effectiveness of peptide drugs.